The pace of change in automation technology continues unabated. Downward pressure on costs, the ever-increasing expectations in terms of process flow and product quality as well as the demand for the most highly flexible production facilities are the market-led driving forces to which the manufacturers of devices, systems and plants are responding with a fast rate of innovation.
Of crucial importance here is the advancement of automation technology, with field buses playing a key role in this technology. Field buses provide an efficient means of transmitting data to various automation devices in order to enable said devices to be controlled on a real-time or virtually real-time basis.
To ensure highly efficient data transmission, various system bus concepts have been developed which are commercially available under the name “Profibus”, “PROFINET”, “Interbus”, “EtherCAT”. The speed of the bus system has been increased by, among other things, transmitting the data in a so-called “broadcast telegram” for which payload data is combined into a packet in order to be then transmitted serially to the individual bus users, instead of transmitting the data individually to individual bus users. In such a system it is possible for the bus users to be disposed in a ring arrangement so that the master-initiated broadcast telegram is transmitted round all the modules, units, etc. This provides the possibility of optimizing the transmission of payload data for a linear structure of this kind.
DE 10 2005 054202 B3, for example, discloses a user device of a serial bus system, a bus system with a user device of this kind and a digital input/output card.
DE 199 22 497 A1 discloses a method for transmitting data between at least two users of a bus system, each user having a logic unit, a memory unit and an interface. After transmission of start information to all the users in the sequence of the consecutive data field positions, data fields are processed position by position by each user writing data to the data field position or positions assigned to it.
WO 03/061211 A1 discloses an installation for transmitting data in a serial bus with a control device which has a transceiver unit for data fields combined to form a data frame, and with bus users which possess an evaluation circuit for reading data fields into and out of the data frame.